Energy-Efficient Low Rank Coal Drying Based on Enhanced Vapor Recompression Technology

Abstract

Vapor recompression is considered a highly energy-efficient technology to recover the heat involved in a process. Unfortunately, in conventional vapor recompression technology, not all of the heat can be recovered effectively. In this study, an enhanced vapor recompression technology enabling more effective heat recovery is proposed, and its ability to dry low rank coal (LRC) is evaluated. We consider the factors of exergy recovery and heat coupling. In addition to conventional vapor recompression, enhanced vapor recompression technology used to dry LRC can recover effectively the sensible heat of dried solid LRC through water recirculation. Moreover, we show that there is an optimum amount of recirculated water for each initial and target moisture content. A temperature–enthalpy diagram reveals that the proposed enhanced vapor recompression technology shows effective heat coupling for each type of heat, which results in less exergy loss so that a marked reduction in energy consumption can be achieved.

Keywords:

• Drying
• Energy efficiency
• Enhanced vapor recompression
• Low rank coal